Allow certain instructions to not be inlined

WasmLib/Decompilation/GenericDecompiler.cs

@@ -112,9 +112,9 @@ namespace WasmLib.Decompilation
                     for (int i = 0; i < parameterEdges.Length; i++) {
                         var edge = parameterEdges[i];
                         var variableNode = edge.Source;
-                        var isPure = !graph.Nodes.OfType<InstructionNode>().Any(x => !x.IsPure & x.Index > variableNode.Index && x.Index < currentNode.Index);
+                        var doesNotSkipImpure = !graph.Nodes.OfType<InstructionNode>().Any(x => !x.IsPure & x.Index > variableNode.Index && x.Index < currentNode.Index);
 
-                        if (isPure) { // TODO: and instruction can be inlined
+                        if (doesNotSkipImpure && variableNode.Instruction.CanBeInlined) {
                             parameters[i] = statements[variableNode.Index];
                             statements.Remove(variableNode.Index);
                         }

WasmLib/Decompilation/Intermediate/Instructions/CallInstruction.cs

@@ -13,6 +13,7 @@ namespace WasmLib.Decompilation.Intermediate.Instructions
         public bool IsIndirect { get; }
         public FunctionSignature Signature { get; }
         public override bool IsPure => false; // TODO: could be optimized by checking if referenced function is pure
+        public override bool CanBeInlined => false; // only for readability
 
         public override ValueKind[] PopTypes => (IsIndirect ? new[] {ValueKind.I32} : new ValueKind[0]).Concat(Signature.Parameters.Reverse()).ToArray();
         public override ValueKind[] PushTypes => Signature.ReturnParameter.Reverse().ToArray();

WasmLib/Decompilation/Intermediate/Instructions/ControlBlockInstruction.cs

@@ -11,6 +11,7 @@ namespace WasmLib.Decompilation.Intermediate.Instructions
         public ControlBlockKind Kind { get; }
         public ValueKind ValueKind { get; }
         public override bool IsPure => false; // TODO: could be optimized by checking if control blocks are pure
+        public override bool CanBeInlined => false;
         
         public ControlBlockInstruction(in Instruction instruction, IReadOnlyList<IntermediateInstruction> block1, IReadOnlyList<IntermediateInstruction>? block2)
         {

WasmLib/Decompilation/Intermediate/Instructions/DropInstruction.cs

@@ -8,5 +8,6 @@ namespace WasmLib.Decompilation.Intermediate.Instructions
         public override ValueKind[] PushTypes => new ValueKind[0];
         public override string OperationStringFormat => "// drop {0}";
         public override bool IsPure => true;
+        public override bool CanBeInlined => false; // inlined behavior would be part of the comment
     }
 }

WasmLib/Decompilation/Intermediate/Instructions/MemoryInstruction.cs

@@ -13,9 +13,8 @@ namespace WasmLib.Decompilation.Intermediate.Instructions
 
         public uint Offset { get; }
         public uint Alignment { get; }
-        
-        // inlining loads would be ugly
-        // public override bool IsPure => Action == ActionKind.Load;
+
+        public override bool IsPure => false;
 
         public MemoryInstruction(in Instruction instruction)
         {

WasmLib/Decompilation/Intermediate/Instructions/UnreachableInstruction.cs

@@ -9,5 +9,7 @@ namespace WasmLib.Decompilation.Intermediate.Instructions
 
         public override string OperationStringFormat => "// UNREACHABLE";
         public override bool RestOfBlockUnreachable => true;
+        public override bool IsPure => false;
+        public override bool CanBeInlined => false;
     }
 }

WasmLib/Decompilation/Intermediate/Instructions/VariableInstruction.cs

@@ -15,6 +15,7 @@ namespace WasmLib.Decompilation.Intermediate.Instructions
         public uint Index { get; }
         public ValueKind Type => Target == TargetKind.Local ? GetLocal(Index) : GetGlobal(Index);
         public override bool IsPure => Action == ActionKind.Get;
+        public override bool CanBeInlined => Action != ActionKind.Tee;
 
         private readonly WasmModule module;
         private readonly FunctionBody body;

WasmLib/Decompilation/Intermediate/IntermediateInstruction.cs

@@ -9,6 +9,7 @@ namespace WasmLib.Decompilation.Intermediate
         public abstract ValueKind[] PushTypes { get; }
         public virtual bool RestOfBlockUnreachable => false;
         public virtual bool IsPure => false;
+        public virtual bool CanBeInlined => true; // only matters if PushTypes has items
         public virtual bool IsImplicit => false;
 
         public bool HasBlock => Block1 != null;